1. Field of the Invention
The present invention relates to an apparatus, a system, a method, and a program for conducting communication of information by using visible light visible for human beings.
2. Description of the Related Art
In the conventional information communication, there have been employed infrared rays and radio waves invisible for the human beings for the following reasons. For example, there does not exist a light emitting device that radiates light with high efficiency, and the visible light is visually uncomfortable and/or visually troublesome for the human beings.
However, with visible light, the human can visually recognize an area or a zone in which the visible light can be received. Therefore, when compared with the infrared rays and the radio waves, the visible light is superior in usability and is more suitable for entertainment depending on purposes of the use thereof. The visible light is the same kind of wave as the radio waves and hence can transmit information.
Recently, as a light source for illumination, a Light Emitting Diode (LED) has rapidly come to broad use in place of the luminescent lamp and the light bulb. By blinking the LED at a high speed at which the blinking cannot be perceived by the human being, it is possible to transmit a large amount of data at an ultra high speed. Thanks to the information communication using the visible light, it is hence possible during the communication to remove various problems occurring in the radio communication and the infrared ray communication. That is, the ubiquitous, omnipresent and ultra high speed communication can be carried out without affecting human bodies and electronic devices.
The articles on techniques associated with and filed before the present invention include, for example, Japanese Patent Application Laid-Open No. 2005-218066 describing a positional information communication apparatus including a positional data section to generate positional information, a modulator section to modulate an electric signal on a power line according to the positional information from the positional data section, and an illumination section to emit illumination light using the electric signal obtained through the modulation. The apparatus communicates the positional information through optical wireless communication by use of illumination light, i.e., visible light.
In addition, Japanese Patent Application Laid-Open No. 2005-260380 describes a cellular phone terminal including a visible light receiving module and a visible light emitting module which are disposed side by side to face the same direction. The terminal carries out visible light communication so that the user visually perceives the visible light employed for the communication.
Additionally, various possibilities of the visible light communication have been described in, for example, “Ubiquitous Visible Light Communications” described by Masao Nakagawa on pages 351 to 359 of the Transactions on Communications of IEICE 2005, B Vol. J-88-B No. 2.
Although Japanese Patent Application Laid-Open Nos. 2005-218066 and 2005-260380 and “Ubiquitous Visible Light Communications” describe the visible light communication to communicate information using visible light including information, consideration has not been given to an operation to control the light emission state of the visible light depending on the communication state.
That is, according to the technique described in these articles, it is not considered that one of the features of the visible light, namely, “visibility, is efficiently utilized.